Forklift Fork Extensions are limited to 150% of the existing fork length.

 The rule governing this limit is generally cited as an OSHA regulation. The fork length requirement is really spelled out in ANSI 56.1-2005, 7.39.1 and additional specifications complete that section of those safety standards. OSHA defers to the ANSI standard, so don't burn your time going thru CFR 1910.178.